Homophily refers to the
tendency for people to have (non-negative) ties with people who are
similar to themselves in socially significant ways. The term itself (due
to Lazarsfeld) specifically refers to an internal preference. However,
today it is usually used to refer to an observable behavioral tendency
whose causes can include preference, but can also include opportunity
(e.g., you have many white friends because most people around you are
white).